If it says each "turn" without any qualifiers, then it activates every hero turn, the environment turn, and the villain turn (Like Pillars of Hercules or Divine Focus). The overall villain-heroes-environment is a round.

Is start phase of villian until end phase of environment a turn? Or...Is there a villian turn, then hero turn, then another hero turn..., then environment turn, then another villian turn?

Or to put it another way, each individual deck plays as a turn. So if a villain has a defensive power that blocks 2 damage from the first attack each turn, for example, it would not reduce any second, third, etc attacks from a given hero, but would "reset" with the next hero and the start of their turn.